The field of the invention is in combined thermal and thermal storage devices.
In many instances it is desirable to maintain a relative constant temperature during interruptions of a primary source of energy. To cite a specific example, infrared sensors when in use must be maintained at a relative low temperature (generally less than 100.degree. K) in order to minimize background noise. Vuilleumier cryogenic refrigerators are commonly used to provide a relatively cold temperature (less than 100.degree. K) with a relatively small cooling capacity (2 to 3 watts) to a relatively small area. Typical Vuilleumier refrigerators utilize electrical energy to operate the motors driving the pistons and to heat the heating element around the end of the hot cylinder. In earth orbiting satellites this electrical energy is supplied from photovoltaic (solar) cells as the primary source and storage batteries are used as a secondary source to supply the electrical energy when the satellite is in the earth's shadow region. The hot cylinder heater element takes a relatively large amount of electrical power and from a space and weight consideration it has been found advantageous to furnish the thermal energy to the hot cylinder when the satellite is in the penumbra and umbra regions by thermal energy storage (TES) material rather than from on-board batteries. This permits the use of a smaller battery system, but in the prior art systems it has added the complications of separately heating the TES material and then conducting the thermal energy from the TES material to the hot cylinder. Heat pipes have been used to conduct heat from a compact heating element to the hot cylinder. All of the prior art devices have been bulky, space consuming, heavy, and of somewhat marginal improvement over battery power.
Typical examples of the prior art may be found in U.S. Pat. Nos. 3,293,409 to C. D. Snelling, 3,356,828 to R. F. Furness, 3,381,113 to D. K. Jacques et al. and 3,624,356 to C. D. Havill.